Derivative Instruments and Hedging Activities (Additional Disclosures) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Dec. 31, 2011
Collateral provided to counterparties:
Offset against derivative liabilities	$ 83				$ 53
Reflected in margin and collateral deposits	96				58
Collateral received from counterparties:
Offset against derivative assets	84				53
Commodity Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Unrealized derivative gains (losses) after taxes recorded in accumulated other comprehensive income	27		21
Interest Rate Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Unrealized derivative gains (losses) after taxes recorded in accumulated other comprehensive income	(47)		(9)
Cash flow hedges | Commodity Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Beginning of period derivative gains (losses)	35	[1]	43	[1]
Effective portion of changes in fair value	30	[1]	8	[1]
End of period derivative gains (losses)	46	[1]	35	[1]
Cash flow hedges | Interest Rate Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Beginning of period derivative gains (losses)	(90)	[1]	(16)	[1]
Effective portion of changes in fair value	12	[1]	2	[1]
End of period derivative gains (losses)	(78)	[1]	(14)	[1]
Cash flow hedges | Competitive power generation revenues | Commodity Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Reclassification to earnings	(19)	[1]	(16)	[1]
Cash flow hedges | Competitive power generation revenues | Interest Rate Contracts
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Reclassification to earnings	0	[1]	0	[1]
Economic hedges | Competitive power generation revenues
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Gain (loss) on derivative instruments	11		6
Economic hedges | Fuel
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Gain (loss) on derivative instruments	5		6
Trading activities | Competitive power generation revenues
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Gain (loss) on derivative instruments	20		16
Electric Utility | Southern California Edison Company | Economic hedges
Derivatives
Realized losses	(55)		(39)
Unrealized losses	(361)		(96)
Collateral already posted, fair value	0				0
Additional collateral, aggregate fair value	67
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Aggregate fair value of all derivative liabilities with credit-risk-related contingent features	285				216
Competitive Power Generation | Edison Mission Group Inc. | Cash flow hedges | Competitive power generation revenues
Accumulated Other Comprehensive Income (Loss) Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges
Amount of gains (losses) for cash flow hedge ineffectiveness	$ 1		$ 2

[1] Unrealized derivative gains (losses) are before income taxes. The after-tax amounts recorded in accumulated other comprehensive loss at March 31, 2012 and 2011 for commodity and interest rate contracts were $27 million and $(47) million, and $21 million and $(9) million, respectively.